EGFR and squamous cell lung carcinoma: Interestingly, in one study, all false-positive results for exon 20 insertions were found in patients with squamous-cell carcinoma that even better visualize the problem of qPCR specificity since EGFR mutations are rare in well-characterized, fully excised surgical specimens of squamous-cell lung carcinoma lacking any adenocarcinoma component (reported frequency of less than 5%) [36,37].